For locally advanced rectal carcinoma,preoperative chemoradiotherapy(CRT) achieved similar overall survival and better local control compared with postoperative therapy,so it was considered to be one of the standard therapy of these patients.But,not every one will be cured,the possible reason is the difference gene expression and mutation status among patients.So,we performed this trial to study the relationship between genetic factors and response of preoperative CRT for locally advanced rectal cancer.